As a method widely used for dissipating the heat generated by heat sources provided, for example, in personal computers, servers and the like, it is practice to use a device comprising a radiant aluminum base plate having one side serving as a heat receiving surface and radiant fins provided on the other side of the plate integrally therewith, by holding the heat receiving surface of the base plate in contact with the heat source and applying a stream of air to the radiant fins with a fan to release the heat emitted by the heat source into the air through the base plate and the fins.
However, personal computers and servers, for example, recently have found an increased number of applications which require high-speed processing, while more multimedia applications such as music and moving video pictures have become available. For this reason, central processing units (hereinafter referred to as “CPUs”), for example, are becoming higher in operating frequency and generate markedly increased amounts of heat. The reduction of noise is also required of such devices. Accordingly, sufficient radiation performance has become no longer available by the method described above, which also fails to achieve the reduction in noise as required.
Also in wide use is a method of releasing heat into the atmosphere utilizing heat pipes with use of a chlorofluorocarbon working fluid for dispersing the heat emitted by heat sources, for example, of industrial machines, tool machines, etc.
Nevertheless, a changeover to cooling systems wherein no chlorofluorocarbon is used has been required from the viewpoint of the protection of the global environment.
To overcome these problems, liquid cooling radiators have been placed into use wherein use is made of a cooing liquid consisting mainly of water, such as an antifreeze solution.
For use in notebook personal computers, a liquid cooling radiator has been proposed which consists of a heat receiving unit comprising a water jacket filled with a cooling liquid and fixed to a heat generating electronic component, and a cooling liquid circulating tube having opposite ends connected to the heat receiving unit for circulating the cooling liquid therethrough. The heat receiving unit and the circulating tube have an antifreeze solution enclosed therein. The heat receiving unit is disposed in the main body of the personal computer which has a keyboard, and the circulating tube extends to a display unit which is openably provided on the main body. The display unit has a corner portion positioned above the main body when the display unit is opened and provided with a reserve tank in communication with the circulating tube (see the publication of JP-A No. 2002-182797). With this liquid cooling radiator, the reserve tank functions to absorb the thermal expansion of the cooling liquid when the liquid is heated with the heat received from the heat source. The reserve tank also serves to replenish the cooling liquid when the amount of the liquid decreases.
For the liquid cooling radiator to achieve an improved cooling efficiency, it is required to remove air in the cooling liquid from the cooling system to the greatest possible extent. However, with the radiator disclosed in the above publication, the air in the reserve tank ingresses into the circulating tube when the display unit is closed, and it is difficult to return the air to the reserve tank when the display unit is opened, so that the radiator has the problem of being lower in cooling efficiency.
An object of the present invention is to solve this problem and to provide an expansion tank device which is adapted to remove the air in the cooling liquid from the circulating system, to prevent the circulating system from breaking and to prevent the decrease in the amount of cooling liquid within the circulating system, the object of the invention further being to provide a process for fabricating the expansion tank device and a liquid cooling radiator.